1. Field of the Invention
The invention relates to a power supply unit which generates a high short-time power in a first mode of operation and a lower continuous power in a second mode of operation, includes an inverter which is connected to a DC voltage source at the input side and to the output of which there is connected, together with a capacitor, a primary winding of a transformer, a secondary winding of which is coupled to a rectifier arrangement. The invention also relates to the use of such a power supply unit in an X-ray generator as well as to an X-ray system including such an X-ray generator.
2. Description of Related Art
An X-ray generator which includes such a power supply unit is known from the patent application U.S. Pat. No. 5,719,759. The inverter operates with a constant frequency which corresponds to the series resonant frequency which results from the capacitance of the capacitor and the leakage inductance of the transformer. During X-ray exposures (with a high short-time power), the power supply unit operates in the first mode of operation whereas it operates in the second mode of operation during X-ray fluoroscopy (with a low continuous power, i.e. a continuously generated low power). The X-ray exposures can be repeated at given time intervals; the temporal mean value that can be reached is then significantly higher than the continuous power that can be reached in the second mode of operation. This continuous power is limited by the thermal loadability of the transformer and the switching elements used in the inverter.